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// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
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package org.apache.doris.nereids.trees.expressions.functions.scalar;

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNotNullable;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.literal.IntegerLiteral;
import org.apache.doris.nereids.trees.expressions.shape.LeafExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.DateTimeV2Type;
import org.apache.doris.nereids.types.IntegerType;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * ScalarFunction 'utc_timestamp'. This class is generated by GenerateFunction.
 */
public class UtcTimestamp extends ScalarFunction
        implements LeafExpression, ExplicitlyCastableSignature, AlwaysNotNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(DateTimeV2Type.SYSTEM_DEFAULT).args(),
            FunctionSignature.ret(DateTimeV2Type.SYSTEM_DEFAULT).args(IntegerType.INSTANCE)
    );

    /**
     * constructor with 0 argument.
     */
    public UtcTimestamp() {
        super("utc_timestamp");
    }

    /**
     * constructor with 1 argument.
     */
    public UtcTimestamp(Expression arg) {
        super("utc_timestamp", arg);
    }

    /** constructor for withChildren and reuse signature */
    private UtcTimestamp(ScalarFunctionParams functionParams) {
        super(functionParams);
    }

    @Override
    public FunctionSignature computeSignature(FunctionSignature signature) {
        signature = super.computeSignature(signature);
        if (arity() == 1 && getArgument(0) instanceof IntegerLiteral) {
            int scale = ((IntegerLiteral) getArgument(0)).getValue();
            if (scale < 0 || scale > 6) {
                throw new AnalysisException("scale must be between 0 and 6");
            }
            return signature.withReturnType(DateTimeV2Type.of(scale));
        }

        return signature;
    }

    @Override
    public void checkLegalityAfterRewrite() {
        if (arity() == 1) {
            if (child(0).isNullLiteral()) {
                throw new AnalysisException("UTC_TIMESTAMP argument cannot be NULL.");
            }
            if (!child(0).isLiteral()) {
                throw new AnalysisException("UTC_TIMESTAMP scale argument must be a constant literal.");
            }
        }
    }

    @Override
    public void checkLegalityBeforeTypeCoercion() {
        checkLegalityAfterRewrite();
    }

    @Override
    public List<FunctionSignature> getSignatures() {
        return SIGNATURES;
    }

    @Override
    public Expression withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.isEmpty() || arity() == 1);
        return new UtcTimestamp(getFunctionParams(children));
    }

    @Override
    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
        return visitor.visitUtcTimestamp(this, context);
    }

    @Override
    public boolean isDeterministic() {
        return false;
    }
}
